That 1000mm combo is pretty good on stationary/slow targets, and not good on fast moving targets, using 1DMkIIN and 1DsMkII. Perhaps on 1DX the combo's AF becomes more responsive, but I haven't checked that yet.

That 1000mm combo is pretty good on stationary/slow targets, and not good on fast moving targets, using 1DMkIIN and 1DsMkII. Perhaps on 1DX the combo's AF becomes more responsive, but I haven't checked that yet.